http://dr.lib.sjp.ac.lk/handle/123456789/35 Sat, 06 Dec 2025 02:06:48 GMT 2025-12-06T02:06:48Z http://dr.lib.sjp.ac.lk/handle/123456789/7003 Broad Absorption Natural Dye (Mondo-Grass berry) for Dye Sensitized Solar Cell De Silva, L.A.; Pitigala, P.K.D.D.P.; Parker, A.G.; Landry, R.; Hasbun, J.E.; Martin, V.; Bandara, T.M.W.T.; Perera, A.G.U. Attached; Two major drawbacks in dye-sensitized solar cells (DSSC) arc the narrow spectral response and the short-term stability. Research on development of artificial dyes for a broad frequency response is a major field of research today. The work presented here shows a broad response with a natural dye extracted from a Mondo-grass iOphiopogon japonicusi berry. Its range of sensitivity covers the entire visible region and its tail expands to the near infrared. This is a unique situation since many natural dyes containing anthocyanin or carotenoids strongly absorbed only below 600 nrn. A Ti02 based electrode sensitized with Mondo grass berry dye DSSC was tested for its performance. An open circuit photovoltage or 495 m V and a short circuit phoiocurrent or 0.6 mJ\/cm7. were obtained under I sun illumination. The broad spectral response from 400 to 750 nm was observed for the Mondo-grass berry dye. A high f II factor of 71 % was achieved but energy conversion efficiency was only 0.2% for the cell. Even though cell efficiency is low with this dye, the solar cells have exhibited better stability when compared with that of the Blackberry. The thin layer chromatography results indicate that Mondo-grass berry dye contains a mixture of two or more chemical compounds belonging to both the .uuhocya nin and the carotenoid families. Mon, 06 Feb 2017 00:00:00 GMT http://dr.lib.sjp.ac.lk/handle/123456789/7003 2017-02-06T00:00:00Z http://dr.lib.sjp.ac.lk/handle/123456789/6978 A low-cost polarimeter for an undergraduate laboratory to study the polarization pattern of skylight Abayaratne, C.P.; Bandara, V. Attached; A simple, low-cost, fully automated polarimeter, which demonstrates fundamental properties of skylight scattering and polarization for undergraduate physics students, is described. The polarimeter includes a microprocessor-based control unit, a Sun tracker, an elevation-azimuth mount with two degrees of freedom, and a polarization sensor unit equipped with a light-dependent resistor for measuring light intensity. Results obtained in the principal plane of the Sun using the polarimeter on a relatively clear day, together with the theoretically expected results for a molecular atmosphere, are presented. A root-mean-square error comparison indicates fairly good agreement between theory and experiment. Construction and experimentation with the polarimeter will provide students with insight into important physical concepts involved in skylight scattering and polarization as well as improve their instrumentation capabilities. Wed, 01 Mar 2017 00:00:00 GMT http://dr.lib.sjp.ac.lk/handle/123456789/6978 2017-03-01T00:00:00Z http://dr.lib.sjp.ac.lk/handle/123456789/6779 Coulomb-enhanced superconducting pair correlations and paired-electron liquid in the frustrated quarter-filled band Gomes, N.; De Silva, W.W.; Dutta, T.; Clay, R.T.; Mazumdar, S. Attached Fri, 01 Jan 2016 00:00:00 GMT http://dr.lib.sjp.ac.lk/handle/123456789/6779 2016-01-01T00:00:00Z http://dr.lib.sjp.ac.lk/handle/123456789/6778 Coulomb enhancement of superconducting pair-pair correlations in a 3 4-filled model for k-(BEDT-TTF)2X De Silva, W.W.; Gomes, N.; Mazumdar, S.; Clay, R.T. Attached; We present the results o f precise correlated-electron calculations on the monomer lattices o f the organic chaige-transfer solids k -(B ED T -T T F)2X for 32 and 64 molecular sites. Our calculations are for band parameters corresponding to X = Cu[N (C N )2]CI and Cu2(C N )3, which are semiconducting antiferromagnetic and quantum spin liquid, respectively, at ambient pressure. We have performed our calculations for variable electron densities p per B E D T -T T F molecule, with p ranging from I to 2. We find that d-wave superconducting pair-pair correlations are enhanced by electron-electron interactions only for a narrow carrier concentration about p = 1.5, which is precisely the carrier concentration where superconductivity in the charge-transfer solids occurs. Our results indicate that the enhancement in pair-pair correlations is not related to antiferromagnetic order, but to a proximate hidden spin-singlet state that manifests itself as a charge-ordered state in other charge-transfer solids. Long-range superconducting order does not appear to be present in the purely electronic model, suggesting that electronphonon interactions also must play a role in a complete theory o f superconductivity. Fri, 01 Jan 2016 00:00:00 GMT http://dr.lib.sjp.ac.lk/handle/123456789/6778 2016-01-01T00:00:00Z